1. Field of the Invention
The subject matter disclosed generally relates to the field of servo writers and disk certifiers for the disks of hard disk drives.
2. Background Information
Hard disk drives contain a plurality of heads that are magnetically coupled to one or more disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disks. The information is typically stored within annular tracks that extend radially across the disks.
The heads are typically mounted to flexure arms that are attached to an actuator arm. The actuator arm includes a voice coil that can move the heads across the disks to access the annular tracks. It is desirable to position the heads at the center of the annular tracks. Deviations from the track centerlines may cause errors in reading and writing data. The heads are centered with a servo routine that utilizes servo bits embedded into the annular tracks.
The servo bits are typically written at the manufacturing facility of a disk drive manufacturer by a system commonly referred to as a servo writer. The servo writer contains electrical circuits that are coupled to the heads of a disk drive. The servo writer causes the heads to write servo bits onto the disks in accordance with a servo writing routine.
Historically, the process of “servowriting” has been performed at the HDA (head-disk-assembly) level of the Hard Disk Drive. Because earlier drives utilized multiple disks and heads, and with fewer servo tracks to write, (due to lower disk data density), servo write time was accomplished in a few minutes. However, the number of servo tracks has continued to increase along with disk data density, and the time required to write and verify all the servo tracks has increased dramatically. Also, because of the data density increases, many hard disk drives today only have a single disk, whereas previously, multiple disks were required. Therefore, for economy of manufacturing, servowriting of multiple disks prior to assembly into the HDA is fast becoming desirable. One manifestation of writing at the disk level, however, is that the same bank of heads is used to write many disks, rather than at the HDA level, where the drive's own heads were used only once to write the servo tracks. Due to wear and tear, the servo-writer heads must be changed periodically.
The heads of a disk drive were historically coupled to a pre-amplifier circuit by soldering two or more twisted wires directly to the flexcircuit. To improve manufacturing efficiencies and high frequency electrical performance, some disk drives utilize flexible circuit boards to couple the heads to the pre-amplifier. A flexible circuit board includes metal traces that are located between a pair of flexible dielectric strips. The traces terminate at contact pads located at the end of the flex circuit. In a hard disk drive, termination to drive electronics is typically done via ultrasonic or laser bonding.
Soldering, ultrasonic or laser bonding of head terminations, however, is simply not acceptable for use at the multiple disk servowriter level due to logistical, cost, and contamination issues. Therefore, in a multiple disk servowriter, it is desirable to couple the heads to servo writer circuits via some sort of electrical connector. Due to severe space limitation, as well as the high number of electrical connections, typically 4 or 5 per head, most commercially available connectors are not applicable. Some prior applications have used spring-biased “pogo” pins for termination to the head flex circuit pads.
However, pogo pins are susceptible to bending and must sometimes be replaced. Additionally, pogo-pin connectors are bulky and difficult to solder onto a corresponding printed circuit board.